How to remove sun ray in photo of a drawing

A friend had a caricature created which she took a picture of but then the original drawing was lost. Fixing this picture of the drawing is outside of my current knowledge base of PS because the problem is the sun was shining down on the drawing across with a wide strip across the face of one of the caricatures.

Any ideas how to remove this?  any of the healing tools and even clone tool will not work in my opinion because there is no referance part of the image to pull from that would replace the face as it was drawn.  I cannot see a tool that would just bring the brightness of that section down to match the rest of the drawing. As it stands, the rest of the drawing will also need adjustments which I can handle but I believe the first glaring issue is the sun shining on this one strip.

Thanks for any advice or terms I can use to search on other potential tools.